Background: Cannabis use has been legalised in four states in USA. However, endocrine effects of marijuana use are largely unknown. Published experiments on animals have suggested that acute cannabis exposure may lead to suppressed thyroid function, but human studies are limited. Of interest, some studies have shown that cannabis has immunomodulatory effects.
Objective and hypotheses: We carried out a cross sectional analysis of data by National Health and Nutrition Examination Survey (NHANES) conducted 20092012 by CDC to assess the relationship between marijuana use and thyroid function, and the prevalence of thyroiditis between recent and nonuser/past users.
Method: We included 1715 adults ages 1745 years who responded to questions related to marijuana use and also had lab results related to thyroid function. Questions were self-administered using the ACASI system, assessing life time marijuana use, timing and frequency of use. We categorized subjects into two groups of i) recent marijuana users (used within 30 days) and ii) past users (older than 30 days) or non-users. Spearman correlations and χ2 tests were used to look at associations between marijuana use and either thyroid function (TSH, total and free T3, and total and free T4) or positivity for thyroglobulin antibody (TBGA) and thyroperoxidase antibody (TPOA).
Results: Total of 53% of the subjects reported lifetime cannabis use with 18% reporting recent use in the last 30 days. There were weak but statistically significant inverse correlations between recent marijuana use and thyroid antibody levels: TPOA (r=−0.07, P=0.003), TBGA (r=−0.05, P=0.02), while free T3 showed a significant positive correlation (r=0.05, P=0.04). Based on the NHANES cut off of 4 IU/ml for positive TBGA, recent marijuana users showed a significantly lower rate of positive TBGA (2.8% vs 6.1%).
Conclusion: Recent marijuana users have a lower prevalence of thyroid autoimmunity. This suggests that marijuana may have immunomodulatory effects. Large prospective studies are needed to confirm this finding.
01 Oct 2015 - 03 Oct 2015